Lymphocyte interactions with endothelial cells

Dual implication of endothelial adhesion molecules in tumor progression and cancer immunity

Adhesion molecules are proteins expressed at the surface of various cell types. Their main contribution to immunity is to allow the infiltration of immune cells in an inflamed site. In cancer, adhesion molecules have been shown to promote tumor dissemination favoring the development of metastasis. While adhesion molecule inhibition approaches were unsuccessful for cancer control, their importance for the generation of an immune response alone or in combination with immunotherapies has gained interest over the past years. Currently, the balance of adhesion molecules for tumor promotion/inhibition is unclear. Here we review the role of selectins, intercellular adhesion molecules (ICAM) and vascular cell adhesion molecules (VCAM) from the perspective of the dual contribution of adhesion molecules in tumor progression and immunity.

Reversal of Endothelial Cell Anergy by T Cell-Engaging Bispecific Antibodies

Objectives: Reduced expression of adhesion molecules in tumor vasculature can limit infiltration of effector T cells. To improve T cell adhesion to tumor endothelial cell (EC) antigens and enhance transendothelial migration, we developed bispecific, T-cell engaging antibodies (bsAb) that activate T cells after cross-linking with EC cell surface antigens. Methods: Recombinant T-cell stimulatory anti-VEGFR2-anti-CD3 and costimulatory anti-TIE2-anti-CD28 or anti-PD-L1-anti-CD28 bsAb were engineered and expressed. Primary lines of human umbilical vein endothelial cells (HUVEC) that constitutively express VEGFR2 and TIE2 growth factor receptors and PD-L1, but very low levels of adhesion molecules, served as models for anergic tumor EC. Results: In cocultures with HUVEC, anti-VEGFR2-anti-CD3 bsAb increased T cell binding and elicited rapid T cell activation. The release of proinflammatory cytokines TNF-α, IFN-γ, and IL-6 was greatly augmented by the addition of anti-TIE2-anti-CD28 or anti-PD-L1-anti-CD28 costimulatory bsAb. Concomitantly, T cell-released cytokines upregulated E-selectin, ICAM1, and VCAM1 adhesion molecules on HUVEC. HUVEC cultured in breast cancer cell-conditioned medium to mimic the influence of tumor-secreted factors were similarly activated by T cell-engaging bsAb. Migration of T cells in transwell assays was significantly increased by anti-VEGFR2-anti-CD3 bsAb. The combination with costimulatory anti-TIE2-anti-CD28 bsAb augmented activation and proliferation of migrated T cells and their cytotoxic capacity against spheroids of the MCF-7 breast cancer cell line seeded in the lower transwell chamber. Conclusions: T cells activated by anti-VEGFR2-anti-CD3 and costimulatory EC-targeting bsAb can reverse the energy of quiescent EC in vitro, resulting in improved T cell migration through an EC layer.

Breg-Mediated Immunoregulation in the Skin

Wound healing is a complex process involving a coordinated series of events aimed at restoring tissue integrity and function. Regulatory B cells (Bregs) are a subset of B lymphocytes that play an essential role in fine-tuning immune responses and maintaining immune homeostasis. Recent studies have suggested that Bregs are important players in cutaneous immunity. This review summarizes the current understanding of the role of Bregs in skin immunity in health and pathology, such as diabetes, psoriasis, systemic sclerosis, cutaneous lupus erythematosus, cutaneous hypersensitivity, pemphigus, and dermatomyositis. We discuss the mechanisms by which Bregs maintain tissue homeostasis in the wound microenvironment through the promotion of angiogenesis, suppression of effector cells, and induction of regulatory immune cells. We also mention the potential clinical applications of Bregs in promoting wound healing, such as the use of adoptive Breg transfer.

Endothelial cell plasticity in kidney fibrosis and disease

Renal endothelial cells demonstrate an impressive remodeling potential during angiogenic sprouting, vessel repair or while transitioning into mesenchymal cells. These different processes may play important roles in both renal disease progression or regeneration while underlying signaling pathways of different endothelial cell plasticity routes partly overlap. Angiogenesis contributes to wound healing after kidney injury and pharmaceutical modulation of angiogenesis may home a great therapeutic potential. Yet, it is not clear whether any differentiated endothelial cell can proliferate or whether regenerative processes are largely controlled by resident or circulating endothelial progenitor cells. In the glomerular compartment for example, a distinct endothelial progenitor cell population may remodel the glomerular endothelium after injury. Endothelial-to-mesenchymal transition (EndoMT) in the kidney is vastly documented and often associated with endothelial dysfunction, fibrosis, and kidney disease progression. Especially the role of EndoMT in renal fibrosis is controversial. Studies on EndoMT in vivo determined possible conclusions on the pathophysiological role of EndoMT in the kidney, but whether endothelial cells really contribute to kidney fibrosis and if not what other cellular and functional outcomes derive from EndoMT in kidney disease is unclear. Sequencing data, however, suggest no participation of endothelial cells in extracellular matrix deposition. Thus, more in-depth classification of cellular markers and the fate of EndoMT cells in the kidney is needed. In this review, we describe different signaling pathways of endothelial plasticity, outline methodological approaches and evidence for functional and structural implications of angiogenesis and EndoMT in the kidney, and eventually discuss controversial aspects in the literature.

Controlled release of vascular endothelial growth factor (VEGF) in alginate and hyaluronic acid (ALG–HA) bead system to promote wound healing in punch-induced wound rat model

For wound healing, angiogenesis is one of the main therapeutic factors for recovering the injured tissue. To address this issue, a combination of two different polymers, alginate (ALG) and hyaluronic acid (HA) in an 80:20 ratio composition is used to optimize the bead system along with the 5 IU heparin (Hep) by crosslinking into calcium chloride (CaCl₂). Encapsulation of Vascular endothelial growth factor (VEGF) in the bead system shows delayed cumulative release in phosphate buffer saline (PBS). For in vitro studies, calf pulmonary artery endothelial (CPAE) cells showed biocompatibility. ALG-HA/VEGF150 improves endothelial Vascular cell adhesion protein 1 (VCAM1) and endothelial nitric oxide synthase (eNOS) expression markers in CPAE cells. In vivo evaluation of the bead system shows around 68% of wound closure 2 weeks post-implantation in 8 mm punch wound models. The treatment group shows decreased epithelial gap between the ends of the wound and neo-epidermal regeneration. ALG-HA/VEGF150 induced significant vascularization, collagen type-1 (Col-1) and fibronectin (FN) development in the in vivo models after 2 weeks of the implantation. Hence, ALG-HA/VEGF150 beads can be used to promote wound healing.

T cell interaction with activated endothelial cells primes for tissue-residency

Tissue-resident memory T cells (TRM) are suspected drivers of chronic inflammation, but their induction remains unclear. Since endothelial cells (EC) are obligate interaction partners for T cells trafficking into inflamed tissues, they may play a role in TRM development. Here, we used an in vitro co-culture system of human cytokine-activated EC and FACS-sorted T cells to study the effect of EC on T(RM) cell differentiation. T cell phenotypes were assessed by flow cytometry, including proliferation measured by CellTrace Violet dilution assay. Soluble mediators were analyzed by multiplex immunoassay. Co-culture of T cells with cytokine-activated, but not resting EC induced CD69 expression without activation (CD25, Ki67) or proliferation. The dynamic of CD69 expression induced by EC was distinct from that induced by TCR triggering, with rapid induction and stable expression over 7 days. CD69 induction by activated EC was higher in memory than naive T cells, and most pronounced in CD8+ effector memory T cells. Early CD69 induction was mostly mediated by IL-15, whereas later effects were also mediated by interactions with ICAM-1 and/or VCAM-1. CD69+ T cells displayed a phenotype associated with tissue-residency, with increased CD49a, CD103, CXCR6, PD-1 and CD57 expression, and decreased CD62L and S1PR1. EC-induced CD69+ T cells were poised for high production of pro-inflammatory cytokines and showed increased expression of T-helper 1 transcription factor T-bet. Our findings demonstrate that activated EC can induce functional specialization in T cells with sustained CD69 expression, increased cytokine response and a phenotypic profile reminiscent of TRM. Interaction with activated EC during transmigration into (inflamed) tissues thus contributes to TRM-residency priming.

Organization of the Skin Immune System and Compartmentalized Immune Responses in Infectious Diseases

The skin is an organ harboring several types of immune cells that participate in innate and adaptive immune responses. The immune system of the skin comprises both skin cells and professional immune cells that together constitute what is designated skin-associated lymphoid tissue (SALT). In this review, I extensively discuss the organization of SALT and the mechanisms involved in its responses to infectious diseases of the skin and mucosa. The nature of these SALT responses, and the cellular mediators involved, often determines the clinical course of such infections. I list and describe the components of innate immunity, such as the roles of the keratinocyte barrier and of inflammatory and natural killer cells. I also examine the mechanisms involved in adaptive immune responses, with emphasis on new cytokine profiles, and the role of cell death phenomena in host-pathogen interactions and control of the immune responses to infectious agents. Finally, I highlight the importance of studying SALT in order to better understand host-pathogen relationships involving the skin and detail future directions in the immunological investigation of this organ, especially in light of recent findings regarding the skin immune system.

Gene expression of human endometrial L-selectin ligand in relation to the phases of the natural menstrual cycle

This study investigates peptide components of L-selectin ligand (LSL) and their gene expressions in human endometrium during the natural menstrual cycle. We recruited 41 endometrial samples from reproductive-aged women with leiomyoma and undergoing hysterectomy and 11 endometrial samples from menopausal women as controls. Immunohistochemistry revealed strong MECA-79 expression from the early through the mid-secretory phase and low expression in menopausal endometrium. Five peptide components of LSL were detected in reproductive and menopausal endometrium by one-step quantitative RT-PCR: podocalyxin, endomucin, nepmucin, GlyCAM-1, and CD34. Endomucin differed significantly between the proliferative and early-secretory phases. CHST2 and CHST4 genes (which are involved in the generation of LSL epitopes) were expressed without significant differences among phases. The gene expression of progesterone receptor decreased from the proliferative to the late-secretory phase, and the difference was significant. However, estrogen receptor α expression showed stability among phases. The significant expression of endomucin between the proliferative and early-secretory phases might play a vital role in endometrial receptivity. Further studies are needed to investigate the factors that regulate the expression of endomucin and other LSL peptide components in different phases of the menstrual cycle.

Focal Adhesion-Independent Cell Migration

Cell migration is central to a multitude of physiological processes, including embryonic development, immune surveillance, and wound healing, and deregulated migration is key to cancer dissemination. Decades of investigations have uncovered many of the molecular and physical mechanisms underlying cell migration. Together with protrusion extension and cell body retraction, adhesion to the substrate via specific focal adhesion points has long been considered an essential step in cell migration. Although this is true for cells moving on two-dimensional substrates, recent studies have demonstrated that focal adhesions are not required for cells moving in three dimensions, in which confinement is sufficient to maintain a cell in contact with its substrate. Here, we review the investigations that have led to challenging the requirement of specific adhesions for migration, discuss the physical mechanisms proposed for cell body translocation during focal adhesion-independent migration, and highlight the remaining open questions for the future.

Abnormal expression of chemokine receptors on T-cells from patients with systemic lupus erythematosus

The expressionof chemokinereceptors on T-cells and chemokinelevels in the blood was studied in 23 patients with SLE (ACR criteria), seven patients with rheumatoid arthritis (RA) and in 15 healthy controls using flow cytometry, RT-PCR and ELISA. The cell surface expression of the chemokine receptors CXCR5 and CCR6 was decreased in SLE patients compared with controls (P 0.051 and P 0.002, respectively). The decrease of CXCR5 was confined to SLE patients with inactive disease (SLEDAI < 6) compared with active disease (SLEDAI ≥6) and controls. CXCR2 and CCR1 were increased in patients with active SLE compared with patients with inactive disease (P 0.001 and P 0.01, respectively) and with controls (P 0.02 and P 0.053, respectively). The levels of the chemokines MIP-1b MCP-1, SDF-1a, IP-10 and RANTES were significantly elevated in SLE patients compared with controls. Patients with renal involvement had increased surface expression of CXCR3 and CCR3 (P 0.04 in both) and a lower level of soluble IP-10 compared with patients without renal disease (P 0.025) and compared with controls (P 0.001). The ratio between CCR5 and CCR3 was significantly increased in RA patients compared with SLE patients and controls supporting a Th1 overweight in RA. In conclusion, patients with SLE showed abnormal T-cell expression of several chemokine receptors and levels of soluble chemokines in their plasma/serum.

The effect of 25(OH)D on endothelial and immunological markers in Behçet's disease

BACKGROUND

Endothelial selectine molecules (ESMs) and Toll-like receptors (TLRs) were suggested to be associated with the pathogenesis of Behçet's disease (BD). 25(OH)D deficiency may be associated with endothelial and immune dysfunction. The aim of this study is to investigate the relationship between the 25(OH)D level, and ESMs and TLRs in BD patients.

PATIENTS AND METHODS

BD patients were classified as 25(OH)D deficient (Group 1) and sufficient (Group 2) groups. Vitamin D replacement therapy was given to Group 1, after the last replacement dose blood was again collected. ESMs and TLRs levels were evaluated and compared both between Group 1 and Group 2, and pre- and post-treatment measurements of Group 1.

RESULTS

The baseline plasma levels of ESMs were significantly higher in Group 1 than in Group 2 (p < 0.05). There were not any significant differences in baseline TLRs levels between Group 1 and Group 2. The mean plasma levels of ESMs were significantly lower in post-replacement assessments (p < 0.05). The mean plasma levels of TLRs were lower in post-replacement assessments, but not significantly (p > 0.05). The active stage disease rate was higher in pre-treatment group (36.3%) than post-treatment group (34.6%), but the difference was not significant (p > 0.05).

CONCLUSION

Although vitamin D replacement in 25(OH)D deficient BD patients may have some beneficial effects on vascular dysfunction, it cannot be considered the primary treatment modality.

Revisiting the role of B cells in skin immune surveillance

Whereas our understanding of the skin immune system has increased exponentially in recent years, the role of B cells in cutaneous immunity remains poorly defined. Recent studies have revealed the presence of B cells within lymphocytic infiltrates in chronic inflammatory skin diseases and cutaneous malignancies including melanoma, and have examined their functional significance in these settings. We review these findings and discuss them in the context of the current understanding of the role of B cells in normal skin physiology, as well as in both animal and human models of skin pathology. We integrate these findings into a model of cutaneous immunity wherein crosstalk between B cells and other skin-resident immune cells plays a central role in skin immune homeostasis.

Transgene and immune gene expression following intramuscular injection of Atlantic salmon (Salmo salar L.) with DNA-releasing PLGA nano- and microparticles

The use of poly-(D,L-lactic-co-glycolic) acid (PLGA) particles as carriers for DNA delivery has received considerable attention in mammalian studies. DNA vaccination of fish has been shown to elicit durable transgene expression, but no reports exist on intramuscular administration of PLGA-encapsulated plasmid DNA (pDNA). We injected Atlantic salmon (Salmo salar L.) intramuscularly with a plasmid vector containing a luciferase (Photinus pyralis) reporter gene as a) naked pDNA, b) encapsulated into PLGA nano- (~320 nm) (NP) or microparticles (~4 μm) (MP), c) in an oil-based formulation, or with empty particles of both sizes. The ability of the different pDNA-treatments to induce transgene expression was analyzed through a 70-day experimental period. Anatomical distribution patterns and depot effects were determined by tracking isotope labeled pDNA. Muscle, head kidney and spleen from all treatment groups were analyzed for proinflammatory cytokines (TNF-α, IL-1β), antiviral genes (IFN-α, Mx) and cytotoxic T-cell markers (CD8, Eomes) at mRNA transcription levels at days 1, 2, 4 and 7. Histopathological examinations were performed on injection site samples from days 2, 7 and 30. Injection of either naked pDNA or the oil-formulation was superior to particle treatments for inducing transgene expression at early time-points. Empty particles of both sizes were able to induce proinflammatory immune responses as well as degenerative and inflammatory pathology at the injection site. Microparticles demonstrated injection site depots and an inflammatory pathology comparable to the oil-based formulation. In comparison, the distribution of NP-encapsulated pDNA resembled that of naked pDNA, although encapsulation into NPs significantly elevated the expression of antiviral genes in all tissues. Together the results indicate that while naked pDNA is most efficient for inducing transgene expression, the encapsulation of pDNA into NPs up-regulates antiviral responses that could be of benefit to DNA vaccination.

Using shape effects to target antibody-coated nanoparticles to lung and brain endothelium

Vascular endothelium offers a variety of therapeutic targets for the treatment of cancer, cardiovascular diseases, inflammation, and oxidative stress. Significant research has been focused on developing agents to target the endothelium in diseased tissues. This includes identification of antibodies against adhesion molecules and neovascular expression markers or peptides discovered using phage display. Such targeting molecules also have been used to deliver nanoparticles to the endothelium of the diseased tissue. Here we report, based on in vitro and in vivo studies, that the specificity of endothelial targeting can be enhanced further by engineering the shape of ligand-displaying nanoparticles. In vitro studies performed using microfluidic systems that mimic the vasculature (synthetic microvascular networks) showed that rod-shaped nanoparticles exhibit higher specific and lower nonspecific accumulation under flow at the target compared with their spherical counterparts. Mathematical modeling of particle-surface interactions suggests that the higher avidity and specificity of nanorods originate from the balance of polyvalent interactions that favor adhesion and entropic losses as well as shear-induced detachment that reduce binding. In vivo experiments in mice confirmed that shape-induced enhancement of vascular targeting is also observed under physiological conditions in lungs and brain for nanoparticles displaying anti-intracellular adhesion molecule 1 and anti-transferrin receptor antibodies.

Proteins and small molecules for cellular regenerative medicine

Regenerative medicine seeks to understand tissue development and homeostasis and build on that knowledge to enhance regeneration of injured tissues. By replenishing lost functional tissues and cells, regenerative medicine could change the treatment paradigm for a broad range of degenerative and ischemic diseases. Multipotent cells hold promise as potential building blocks for regenerating lost tissues, but successful tissue regeneration will depend on comprehensive control of multipotent cells-differentiation into a target cell type, delivery to a desired tissue, and integration into a durable functional structure. At each step of this process, proteins and small molecules provide essential signals and, in some cases, may themselves act as effective therapies. Identifying these signals is thus a fundamental goal of regenerative medicine. In this review we discuss current progress using proteins and small molecules to regulate tissue regeneration, both in combination with cellular therapies and as monotherapy.

In vivo modulation of the inflammatory response by nonsteroidal antiinflammatory drug-related compounds that trigger L-selectin shedding

Diphenylamine-based nonsteroidal antiinflammatory drugs (NSAIDs) are able to cause in vitro the shedding of L-selectin. The aim of this work was to determine the physio-logic relevance of L-selectin shedding in the antiinflammatory effect exerted by NSAIDs in vivo. Chemical compounds structurally related to NSAIDs - including diphenyl-amine, N-phenylanthranilic acid (N-Ph), diphenylacetic acid - as well as the traditional NSAID indomethacin were studied using the zymosan air-pouch mouse model. Animals intramuscularly pretreated with indomethacin or N-Ph, but not with diphenyl-amine or diphenylacetic acid, showed a significant dose-dependent reduction in the number of neutrophils compared with untreated animals (N-Ph, IC50 = 6.7 mg/kg). Except for indomethacin, none of these compounds caused any significant reduction in cyclooxygenase-1 activity in vivo. In flow chamber experiments, N-Ph reduced the capability of human neutrophils to pass across the endothelial barrier by interfering with leukocyte rolling step on HUVEC. N-Ph, but not diphenylacetic acid, induced activation-independent L-selectin shedding in mouse neutrophils. Interestingly, N-Ph exerted an antiinflammatory effect similar to that of the anti-L-selectin blocking antibody Mel-14, although no additive action was observed when both compounds were combined. These data suggest that the L-selectin shedding induced by NSAIDs may be involved in the antiinflammatory action exerted by these compounds in clinical settings.

Pattern of adhesion molecule expression in labial salivary glands from patients with primary Sjögren's syndrome

The aim of this work was to examine the pattern of distribution of adhesion molecules in minor salivary glands from patients with primary Sjögren's syndrome (SS). Labial salivary gland (LSG) biopsies from 31 patients with primary SS and 21 normal subjects were examined. Cryostat sections were examined with monoclonal antibodies to different adhesion molecules using an indirect immunoperoxidase technique. There was an increased expression of ICAM-1, class IMHC, HLA-DR & DQ (p<0.05) on endothelial cells, lymphocytes, fibroblasts and salivary epithelial cells (HLA-DR far exceeds ICAM-1 (limited) epithelial expression). ELAM-1 and to a lesser extent VCAM-1 were demonstrated over some of the endothelial cells in patients, but not in controls (p<0.01). Many of the endothelial cells expressing ICAM-1, DR, DQ, ELAM-1 were high endothelial venules. CD44 was strongly expressed over epithelial cells, endothelial and infiltrating mononuclear cells, while LFA-3 was present mainly on epithelial cells, and faintly on infiltrating inflammatory cells. There was no difference between patients and controls with regard to CD44 or LFA-3 expression. The ligands for the above mentioned adhesion molecules, namely LFA-1α, LFA-1ß, LECAM-1, VLA-4ß(CD49d), CD44 and CD2 were demonstrated (variably) on the surface of infiltrating lymphocytes. CD11b and CD11c were detected over monocytes/macrophages. A proportion of lymphocytes expressed VCAM-1 and CD11c and may function as antigen presenting cells. In some biopsies these molecules were localized at the center of lymphoid follicles with the appearance of dendritic cells. Although the majority of lymphocytes were activated and strongly expressing DR and ICAM-1, they were IL-2Rα (CD25) negative. We conclude that adhesion molecules are prominent in LSG of patients with primary SS. They may play a major role by mediating the lymphocytic infiltration to the glands, retaining the lymphocytes in the glands and regulating the different immune responses in the local microenvironment of this chronic inflammatory disease.

Contribution of 4-1BBL on radioresistant cells in providing survival signals through 4-1BB expressed on CD8⁺ memory T cells in the bone marrow

The persistence of memory lymphocytes is a critical feature of adaptive immunity. The TNF family ligand 4-1BBL supports the antigen-independent survival of CD8⁺ memory T cells. Here, we show that mice lacking 4-1BB only on αβ T cells show a similar defect in CD8⁺ T-cell recall responses, as previously shown in 4-1BBL-deficient mice. We show that 4-1BB is selectively expressed on BM CD8⁺ but not CD4⁺ memory T cells of unimmunized mice. Its ligand, 4-1BBL, is found on VCAM-1⁺ stromal cells, CD11c⁺ cells, and a Gr1(lo) myeloid population in unimmunized mice. Adoptive transfer of in vitro generated memory T cells into mice lacking 4-1BBL only on radioresistant cells recapitulates the defect in CD8⁺ T-cell survival seen in the complete knockout mice, with smaller effects of 4-1BBL on hematopoietic cells. In BM, adoptively transferred DsRed CD8⁺ memory T cells are most often found in proximity to VCAM-1⁺ cells or Gr1⁺ cells, followed by B220⁺ cells and to a much lesser extent near CD11c⁺ cells. Thus, a VCAM-1⁺CD45(-) stromal cell is a plausible candidate for the radioresistant cell that provides 4-1BBL to CD8⁺ memory T cells in the BM.

Chemokines: structure, receptors and functions. A new target for inflammation and asthma therapy?

Five to 10% of the human population have a disorder of the respiratory tract called 'asthma'. It has been known as a potentially dangerous disease for over 2000 years, as it was already described by Hippocrates and recognized as a disease entity by Egyptian and Hebrew physicians. At the beginning of this decade, there has been a fundamental change in asthma management. The emphasis has shifted from symptom relief with bronchodilator therapies (e.g. beta(2)-agonists) to a much earlier introduction of anti-inflammatory treatment (e.g. corticosteroids). Asthma is now recognized to be a chronic inflammatory disease of the airways, involving various inflammatory cells and their mediators. Although asthma has been the subject of many investigations, the exact role of the different inflammatory cells has not been elucidated completely. Many suggestions have been made and several cells have been implicated in the pathogenesis of asthma, such as the eosinophils, the mast cells, the basophils and the lymphocytes. To date, however, the relative importance of these cells is not completely understood. The cell type predominantly found in the asthmatic lung is the eosinophil and the recruitment of these eosinophils can be seen as a characteristic of asthma. In recent years much attention is given to the role of the newly identified chemokines in asthma pathology. Chemokines are structurally and functionally related 8-10 kDa peptides that are the products of distinct genes clustered on human chromosomes 4 and 17 and can be found at sites of inflammation. They form a superfamily of proinflammatory mediators that promote the recruitment of various kinds of leukocytes and lymphocytes. The chemokine superfamily can be divided into three subgroups based on overall sequence homology. Although the chemokines have highly conserved amino acid sequences, each of the chemokines binds to and induces the chemotaxis of particular classes of white blood cells. Certain chemokines stimulate the recruitment of multiple cell types including monocytes, lymphocytes, basophils, and eosinophils, which are important cells in asthma. Intervention in this process, by the development of chemokine antagonists, might be the key to new therapy. In this review we present an overview of recent developments in the field of chemokines and their role in inflammations as reported in literature.

The Role of the Endothelium in HPS Pathogenesis and Potential Therapeutic Approaches

American hantaviruses cause a highly lethal acute pulmonary edema termed hantavirus pulmonary syndrome (HPS). Hantaviruses nonlytically infect endothelial cells and cause dramatic changes in barrier functions of the endothelium without disrupting the endothelium. Instead hantaviruses cause changes in the function of infected endothelial cells that normally regulate fluid barrier functions of capillaries. The endothelium of arteries, veins, and lymphatic vessels is unique and central to the function of vast pulmonary capillary beds, which regulate pulmonary fluid accumulation. The endothelium maintains vascular barrier functions through a complex series of redundant receptors and signaling pathways that serve to both permit fluid and immune cell efflux into tissues and restrict tissue edema. Infection of the endothelium provides several mechanisms for hantaviruses to alter capillary permeability but also defines potential therapeutic targets for regulating acute pulmonary edema and HPS disease. Here we discuss interactions of HPS causing hantaviruses with the endothelium, potential endothelial cell-directed permeability mechanisms, and therapeutic targeting of the endothelium as a means of reducing the severity of HPS disease.

Lipoxin A4 inhibits immune cell binding to salivary epithelium and vascular endothelium

Lipoxins are formed by leukocytes during cell-cell interactions with epithelial or endothelial cells. Native lipoxin A(4) (LXA(4)) binds to the G protein-coupled lipoxin receptors formyl peptide receptor 2 (FPR2)/ALX and CysLT1. Furthermore, LXA(4) inhibits recruitment of neutrophils, by attenuating chemotaxis, adhesion, and transmigration across vascular endothelial cells. LXA(4) thus appears to serve as an endogenous "stop signal" for immune cell-mediated tissue injury (Serhan CN; Annu Rev Immunol 25: 101-137, 2007). The role of LXA(4) has not been addressed in salivary epithelium, and little is known about its effects on vascular endothelium. Here, we determined that interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) receptor activation in vascular endothelium and salivary epithelium upregulated the expression of adhesion molecules that facilitates the binding of immune cells. We hypothesize that the activation of the ALX/FPR2 and/or CysLT1 receptors by LXA(4) decreases this cytokine-mediated upregulation of cell adhesion molecules that enhance lymphocyte binding to both the vascular endothelium and salivary epithelium. In agreement with this hypothesis, we observed that nanomolar concentrations of LXA(4) blocked IL-1β- and TNF-α-mediated upregulation of E-selectin and intercellular cell adhesion molecule-1 (ICAM-1) on human umbilical vein endothelial cells (HUVECs). Binding of Jurkat cells to stimulated HUVECs was abrogated by LXA(4). Furthermore, LXA(4) preincubation with human submandibular gland cell line (HSG) also blocked TNF-α-mediated upregulation of vascular cell adhesion molecule-1 (VCAM-1) in these cells, and it reduced lymphocyte adhesion. These findings suggest that ALX/FPR2 and/or CysLT1 receptor activation in endothelial and epithelial cells blocks cytokine-induced adhesion molecule expression and consequent binding of lymphocytes, a critical event in the pathogenesis of Sjögren's syndrome (SS).

Physiology and pathophysiology of selectins, integrins, and IgSF cell adhesion molecules focusing on inflammation. A paradigm model on infectious endocarditis

The development of adhesion bonds, either among cells or among cells and components of the extracellular matrix, is a crucial process. These interactions are mediated by some molecules collectively known as adhesion molecules (CAMs). CAMs are ubiquitously expressed proteins playing a central role in controlling cell migration, proliferation, survival, and apoptosis. Besides their key function in physiological maintenance of tissue integrity, CAMs play an eminent role in various pathological processes such as cardiovascular disorders, atherogenesis, atherosclerotic plaque progression and regulation of the inflammatory response. CAMs such as selectins, integrins, and immunoglobulin superfamily take part in interactions between leukocyte and vascular endothelium (leukocyte rolling, arrest, firm adhesion, migration). Experimental data and pathologic observations support the assumption that pathogenic microorganisms attach to vascular endothelial cells or sites of vascular injury initiating intravascular infections. In this review a paradigm focusing on cell adhesion molecules pathophysiology and infective endocarditis development is given.

Changes in plasma levels of soluble E-selectin, T lymphocyte subsets and NK cells in patients with chronic HBV infection

AIM: To evaluate serum and hepatic levels of E-selectin in patients with chronic HBV infection and to analyze their relationship with T lymphocyte subsets and natural killer (NK) cells.

METHODS: Serum samples from 270 patients with chronic HBV infection, including 101 patients with chronic hepatitis, 121 with liver cirrhosis and 48 with hepatocellular carcinoma, and from 281 healthy controls, were used in this study. Circulating levels of soluble E-selectin were measured by enzyme-linked immunosorbent assay (ELISA). T lymphocyte subsets and NK cells were measured by flow cytometry (FCM). Immunohistochemistry (IHC) was used to detect the expression of E-selectin in liver tissue specimens from patients with chronic HBV infection.

RESULTS: Serum levels of soluble E-selectin were higher in patients with chronic hepatitis or liver cirrhosis than in those with hepatocellular carcinoma and healthy controls (68.94 ± 34.09, 43.39 ± 18.00 vs 16.69 ± 8.27, 13.96 ± 7.50, all P < 0.01). Immunohistochemistry analysis showed that the positive rates of E-selectin expression in endothelial cells in patients with chronic hepatitis and those with liver cirrhosis were 83.3% and 57.1% (χ² = 6.242, P = 0.012), respectively, and no positive E-selectin staining was detected in patients with hepatocellular carcinoma or healthy controls. The percentages of CD4⁺ T cells and NK cells decreased significantly in patients with chronic HBV infection than in controls (29.11 ± 6.79 vs 37.02 ± 7.05; 23.57 ± 7.33 vs 27.37 ± 7.03, both P < 0.01). The percentages of CD3⁺, CD8⁺, CD4⁺ T cells and NK cells decreased significantly in patients with liver cirrhosis or hepatocellular carcinoma than in controls (all P < 0.01). Soluble E-selectin levels were positively related to the percentages of CD3⁺ and CD8⁺ cells (r = 0.548, 0.715; both P < 0.01), but negatively related to the percentages of CD4+ cells and NK cells (r = -0.429, -0.672; both P < 0.01).

CONCLUSION: Varying degrees of immune dysfunction is present in patients with chronic HBV infection, and high expression of E-selectin is associated with the development of chronic hepatitis and liver cirrhosis. These results suggest that E-selectin can be used as a useful marker for evaluation of hepatic inflammatory activity.

Anaphylaxis and mortality induced by treatment of mice with anti-VLA-4 antibody and pertussis toxin

Ab-mediated blockade of the adhesion molecule VLA-4 has been shown to ameliorate disease in human multiple sclerosis patients and experimental autoimmune encephalomyelitis (EAE) animal models. We wanted to determine whether anti-VLA-4 Ab treatment affected the function and persistence of autoreactive T cells in mice with EAE. Unexpectedly, we observed a high level of mortality in anti-VLA-4 mAb (PS/2)-treated mice with actively induced EAE despite decreased disease severity. Investigation of the underlying mechanism showed that injection of PS/2 mAb in combination with pertussis toxin resulted in anaphylaxis and mortality. Furthermore, the data showed that CD4(+) T cells were required for this effect and suggested a role for IL-1β and TNF-α in the underlying pathology. The results reveal a previously not appreciated deleterious effect of anti-VLA-4 Ab treatment in combination with exposure to pertussis toxin.

Differential expression of cell adhesion molecules in the functional compartments of lymph nodes and tonsils

Aims-To analyse the topographical distribution of adhesion molecules involved in lymphocyte recirculation in human lymph nodes and tonsils. The study focused on the expression of LECAM-1 (CD62L), VLA-alpha4 (CD49d), VLA-beta1 (CD29), LFA-1 alphaL (CD11a), LFA-beta2 (CD18), VCAM-1 (CD106), ICAM-1 (CD54), and H-CAM (CD44).Methods-Reactive lymph nodes and palatine tonsils were studied using immunofluorescence methods with fluorescein isothiocyanate (FITC) labelled monoclonal antibodies directed against cell adhesion molecules. To investigate the expression patterns of these molecules in the T and B cell populations, double labelling experiments were performed using Texas Red labelled antibodies against CD2 or CD19, respectively. The images from each fluorochrome were then simultaneously analysed using a laser scanning confocal microscope.Results-LECAM-1, VLA-alpha4 and H-CAM were predominantly expressed by mantle zone B cells, VCAM-1 and ICAM-1 by germinal centre cells, most of which exhibited a reticular staining pattern suggestive of follicular dendritic cells, whereas LFA-1 alphaL and LFA-beta2 were mainly found in extrafollicular and germinal centre T cells. All high endothelial venules expressed VLA-beta1 and ICAM-1, whereas VCAM-1 was present in only a few, with variable intensity.Conclusions-The data show that all of these adhesion molecules are differentially distributed within the distinct functional microenvironments of both organs. The differences observed in the expression patterns among the B and T cells belonging to different compartments probably depend on the momentum of cell traffic, the stage of maturation/activation, as well as on their functional role in the immune response.

Acute myeloid leukemia with infiltration of thyroid gland complicating Hashimoto's thyroiditis

We describe a case of acute myeloid leukemia with infiltration of thyroid gland complicating Hashimoto's thyroiditis. In Hashimoto's thyroiditis, the leukocyte function-associated antigen-1 (LFA-1)/intercellular vascular cell adhesion molecule-1 (ICAM-1) and very late antigen-4 (VLA-4)/vascular cell adhesion molecule-1 (VCAM-1) pathways in T lymphocytes and the vascular endothelium both play a role in the initiation and enhancement of lymphocyte recruitment to the thyroid glands during an autoimmune attack. The leukemic blast cells were positive for VLA-4 and negative for LFA-1 by immunohistochemistry. The presence of VLA-4 in blast cells might play a key role in the migration of blast cells to the thyroid glands.

Circulating adhesion molecules and purine nucleotides during kidney allograft reperfusion

The impairment of organ function due to ischemia-reperfusion injury is still an important problem in solid organ transplantation. Numerous experimental and clinical studies of native organs have shown that ischemia-reperfusion constitutes an acute inflammatory process involving cell surface adhesion molecule expression. These markers are crucial for the recruitment and infiltration of effector cells into the postischemic tissue. Purines released by the postischemic tissue as the products of the degradation of high-energy nucleotides can be regarded as markers of disturbed energy metabolism. The aim of this study was to examine the correlation between circulating adhesion molecules and purine metabolites in graft renal vein plasma during 49 cases of kidney reperfusion. E-selectin, ICAM-1, and VCAM-1 concentrations correlated positively with hypoxanthine concentrations during reperfusion, whereas the concentrations of ICAM-1 correlated negatively with xanthine concentrations. The results of the present study suggested that the concentrations of adhesion molecules in the renal vein during reperfusion correlated with purine metabolites, reflecting metabolic changes in renal tissue.

Functional knockdown of VCAM-1 at the posttranslational level with ER retained antibodies

Vascular cell adhesion molecule 1 (VCAM-1) is involved in the recruitment of leukocytes to inflammatory sites. In this study we present the first functional knockdown of VCAM-1 using an ER retained antibody construct. We generated a knockdown construct encoding the VCAM-1 specific single chain variable fragment scFv6C7.1 fused to the C-terminal ER retention sequence KDEL. HEK-293:VCAM-YFP cells stably expressing a VCAM-YFP fusion protein were transiently transfected with the knockdown construct and showed down-regulation of surface VCAM-1. Knockdown efficiency of the system is time-dependent due to used transient transfection of the intrabody construct. Furthermore, intrabody mediated knockdown of HEK-293:VCAM-YFP cells also impaired cell-cell interaction with Jurkat cells that are endogenously expressing VLA-4, the physiological partner of VCAM-1. Posttranslational knockdown with ER retained antibodies seems to be a promising technique, as shown here for VCAM-1.

Enrichment of distinct microfilament-associated and GTP-binding-proteins in membrane/microvilli fractions from lymphoid cells

Lymphocyte microvilli mediate initial adhesion to endothelium during lymphocyte transition from blood into tissue but their molecular organization is incompletely understood. We modified a shear-based procedure to prepare biochemical fractions enriched for membrane/microvilli (MMV) from both human peripheral blood T-lymphocytes (PBT) and a mouse pre-B lymphocyte line (300.19). Enrichment of proteins in MMV relative to post nuclear lysate was determined by LC/MS/MS analysis and label-free quantitation. Subsequent analysis emphasized the 291 proteins shared by PBT and 300.19 and estimated by MS peak area to be highest abundance. Validity of the label-free quantitation was confirmed by many internal consistencies and by comparison with Western blot analyses. The MMV fraction was enriched primarily for subsets of cytoskeletal proteins, transmembrane proteins and G-proteins, with similar patterns in both lymphoid cell types. The most enriched cytoskeletal proteins were microfilament-related proteins NHERF1, Ezrin/Radixin/Moesin (ERMs), ADF/cofilin and Myosin1G. Other microfilament proteins such as talin, gelsolin, myosin II and profilin were markedly reduced in MMV, as were intermediate filament- and microtubule-related proteins. Heterotrimeric G-proteins and some small G-proteins (especially Ras and Rap1) were enriched in the MMV preparation. Two notable general observations also emerged. There was less overlap between the two cells in their transmembrane proteins than in other classes of proteins, consistent with a special role of plasma membrane proteins in differentiation. Second, unstimulated primary T-lymphocytes have an unusually high concentration of actin and other microfilament related proteins, consistent with the singular role of actin-mediated motility in the immunological surveillance performed by these primary cells.

Biological responses to chemokine superfamily members

A detailed summary of all the chemokine subfamily members including alternative names, receptor-ligand pairs, receptor cellular distribution, and leukocyte responsiveness is presented here along with assays to measure the biological activities of chemokines on each of the major leukocyte subsets (i.e., microchemotaxis chambers, fluorescence-based assays, use of nitrocellulose filters and membranes coated with extracellular matrix proteins, cellular adhesion assays, mobilization of intracellular free calcium, actin polymerization, degranulation assays, and the use of chemokine receptor-specific antibodies in flow cytometric analysis and radiolabeled chemokine binding assays).

IL-15 regulates immature B-cell homing in an Ly49D-, IL-12–, and IL-18–dependent manner

To complete their maturation and participate in the humoral immune response, immature B cells that leave the bone marrow are targeted to specific areas in the spleen, where they differentiate into mature cells. Previously, we showed that immature B cells actively down-regulate their integrin-mediated migration to lymph nodes or to sites of inflammation, enabling their targeting to the spleen for final maturation. This inhibition is mediated by IFN-γ, which is transcribed and secreted at low levels by these immature B cells; IFN-γ expression is extinguished following B-cell maturation. Stimulation of the MHC class I receptor, Ly49D, triggers a signaling cascade that increases transcription of both IL-12 (p40) and IL-18; these, in turn, induce the secretion of IFN-γ. In the present study, we demonstrate that Ly49D-dependent secretion of IL-12 and IL-18 induces IL-15 expression by immature B cells, and that these 3 factors together regulate IFN-γ production that inhibits their ability to home to the lymph nodes or to sites of inflammation. Thus, IL-15 controls immature B-cell homing, resulting in shaping the B-cell repertoire to enable an efficient immune response.

Immunology

The concept of forbidden foods that should not be eaten goes back to the Garden of Eden and apart from its religious meanings it may also have foreshadowed the concept of foods that can provoke adverse reactions. Thus we could say that allergic diseases have plagued mankind since the beginning of life on earth. The prophet Job was affected by a condition that following the rare symptoms described by the Holy Bible might be identified as a severe form of atopic dermatitis (AD). The earliest record of an apparently allergic reaction is 2621 B.C., when death from stinging insects was first described by hieroglyphics carved into the walls of the tomb of Pharaoh Menes depicting his death following the sting of a wasp. In 79 A.D., the death of the Roman admiral Pliny the Elder was ascribed to the SO₂-rich gases emanating from the eruption of Mount Vesuvius. Hippocrates (460–377 B.C.) was probably the first to describe how cow’s milk (CM) could cause gastric upset and hives, proposing dietetic measures including both treatment and prevention for CM allergy.

IL-12 and IL-18 down-regulate B cell migration in an Ly49D-dependent manner

In order to complete their maturation and participate in the humoral immune response, immature B cells that leave the bone marrow are targeted to specific areas in the spleen, where they differentiate into mature cells. Previously, we showed that immature B cells actively down-regulate their integrin-mediated migration to LN or to sites of inflammation, enabling their targeting to the spleen. This inhibition is mediated by IFN-gamma, which is transcribed and secreted at low levels by these immature B cells; its expression is subsequently down-regulated following B cell maturation. The activating and inhibitory MHC class I receptors, Ly49D and Ly49G2, regulate IFN-gamma secretion in B cells, preventing their migration to antigen-enriched sites and their premature encounter with an antigen, while enabling their entry into the LN when mature. In the present study, we elucidate the pathways by which the Ly49 receptors regulate IFN-gamma levels. We show that Ly49D stimulation triggers a signaling cascade that increases transcription of both IL-12B and IL-18; these, in turn, can interact with their specific receptors, which are expressed at elevated levels on immature B cells. Ligation of the IL-12B and IL-18 receptors induces the secretion of IFN-gamma, thereby regulating their cytoskeleton rearrangement and migration.

EFFECT OF ARGININE ON CELLULAR ADHESION MOLECULE EXPRESSION AND LEUKOCYTE TRANSMIGRATION IN ENDOTHELIAL CELLS STIMULATED BY BIOLOGICAL FLUID FROM SURGICAL PATIENTS

This study investigated the effect of different arginine (Arg) concentrations on adhesion molecule expression on endothelial cells (ECs) and leukocytes and the transendothelial migration of polymorphonuclear neutrophils (PMNs) through ECs stimulated by plasma or peritoneal drain fluid (PDF) from surgical patients. Human umbilical vein ECs (HUVECs) and PMNs from healthy subjects were treated with different concentrations (0, 50, 100, and 1000 micromol/L) of Arg for 24 h. After that, HUVECs were stimulated for 3 h with plasma or PDF from patients who underwent abdominal surgery, and PMNs were allowed to transmigrate through ECs for 2 h. The HUVEC expression of cellular adhesion molecules (CAMs) and integrin (CD11b) and the interleukin (IL) 8 receptor expression on PMNs were measured by flow cytometry. The PMNs transmigrating through ECs were also analyzed. The results showed that CAM and integrin expressions in PDF groups were higher than those in control groups. Among the PDF groups, IL-8 secretions from ECs and PMNs were lower with 100 and 1000 micromol/L Arg than with 0 and 50 micromol/L Arg, and this was consistent with the expression of the IL-8 receptor on PMNs. In addition, CAM expressions on ECs and CD11b expression on PMNs, as well as PMN transmigration, were lower with 100 and 1000 micromol/L Arg than with 0 and 50 micromol/L Arg. The HUVECs stimulated by plasma from surgical patients had similar effects on surface molecule expression as PDF; however, as shown in PDF stimulation, the effects were not so obvious. Inhibition of nitric oxide production results in high CAM and IL-8 expressions comparable with groups with low Arg administration. The results of this in vitro study suggest that ECs and PMNs were activated after patients' plasma or PDF stimulation. A low Arg concentration comparable with catabolic conditions resulted in higher adhesion molecule expression and greater transendothelial migration of neutrophils. Arginine administration at levels similar to or higher than physiological concentrations reduced IL-8 and CAM expression, and PMN transmigration was also decreased after stimulation with plasma or PDF from surgical patients. Inactivation of NO results in high CAM and IL-8 expression. This finding indicated that NO may be an important endogenous inhibitor for EC-PMN interaction and neutrophil transmigration.